Process Modeling
Fundamentals
Three Ways to Understand a System
By its processes

What are the systems main processes?
By its data

What data does the system maintain?
By its output

What output will the system produce?
All 3 should be consistent with each other.
When is Process Modeling done?
Process Modeling is part of the requirements Structuring Stage.
We create process, logic and data models based on information gathered during
the Requirements Determination stage (through interviews, surveys, etc.).
In this way, requirements structuring helps guide us through determination, e.g.
knowing what questions to ask in interviews.
Learning Objectives
How to model organizational processes
and the data they use, store and produce
Understand rules and guidelines for
drawing data flow diagrams
How to decompose data flow diagrams
into lower-level diagrams
Rules of balancing data flow diagrams
Learning Objectives
Explain the differences among four types
of DFDs: current physical, current logical,
new physical and new logical
Discuss the use of data flow diagrams as
analysis tools
What is Process Modeling?
A way to graphically represent the system under
study as processes that capture, manipulate,
store and distribute data between a system and
its environment and among system components
There are many techniques that can be used for
modeling processes

Structured analysis and design models processes
with data flow diagrams (DFDs)
Data flow diagrams are a way to graphically illustrate
movement of data between external entities outside the
system and the processes and data stores within a system
Process Modeling
Some deliverables and outcomes for
current and proposed system


Context data flow diagram
Logical DFDs
Level 0, level 1’s, etc.
Technology independent
Show data flows, structure and functional
requirements of system


Processing logic
Project dictionary and CASE repository
Four Types of Process Models
Current
Proposed
Logical
Physical aspects of system are removed
as much as possible
Current system is reduced to data and
processes that transform them
Includes additional functions
Obsolete functions are
removed
Inefficient data flows are
reorganized
Physical
Process label includes an identification
of the technology (people or systems)
used to process the data
Data flows and data stores are labeled
with the actual name of the physical
media on which data flow or in which
data are stored
Represents the physical
implementation of the new
system
Guidelines for Drawing DFDs
Completeness


DFD must include all components necessary
for system
Each component must be fully described in
the project dictionary or CASE repository
Consistency

8.9
The extent to which information contained on
one level of a set of nested DFDs is also
included on other levels
Guidelines for Drawing DFDs
Timing


Time is not represented well on DFDs
Best to draw DFDs as if the system has never
started and will never stop.
Iterative Development

8.10
Analyst should expect to redraw diagram
several times before reaching the closest
approximation to the system being modeled
Guidelines for Drawing DFDs
Primitive DFDs


8.11
Lowest logical level of decomposition
Decision has to be made when to stop
decomposition